Two reporters central to revealing the massive US government surveillance effort returned to the United States for the first time since the story broke and used the occasion to praise their exiled source: Edward Snowden.

Glenn Greenwald and Laura Poitras became a story of their own amid speculation they could be arrested upon arriving at New York's Kennedy airport. They were instead confronted by only reporters and photographers before fighting through traffic en route to a Manhattan hotel to receive a George Polk Award for national security reporting.

In remarks before an audience of other journalists and editors, the pair credited the courage of Snowden, the former NSA contractor who leaked the information for their story.

"This award is really for Edward Snowden," Poitras said.

Greenwald and Poitras had flown to Hong Kong to meet Snowden after the former defence contractor fled to the city with his leaked materials.

Greenwald said: "I hope that as journalists we realise not only the importance of defending our own rights, but also those of our sources like Edward Snowden."

The pair shared the award with The Guardian's Ewen MacAskill and Barton Gellman of The Washington Post.

At the airport, Greenwald said he and Poitras were not "100 per cent sure" they could enter the US without being arrested. He said lawyers had sought assurance from the US Justice Department "and they purposefully wouldn't give them any information about whether we were the target of a grand jury or whether there was already an indictment that was under seal". Still, Greenwald said he "expected that they wouldn't be that incredibly stupid and self-destructive to try and do something that in the eyes of the world would be viewed as incredibly authoritarian".

Greenwald said he still regularly speaks to Snowden, who was granted asylum in Russia for a year. He said Snowden was aware of the award and "was very supportive of that".

Peter King, who leads the House of Representatives' Homeland Security subcommittee on counterterrorism and intelligence, called Greenwald "a disgrace to journalism and the country", adding: "No American should give Glenn Greenwald an award for anything."